Expansion joint



Patented June 5, 19328.

'narra-D STATES PATENT- orne-E.

ROBERT c. SCOTT, or aannemen, MAssAoHnsETTs.

Exrnlvsrorr JOINT.

lApplication led yJune I1, 11925. SeriaINo. 33,939.

The :invention tto be 'hereinafter described relates to kexpansion joints Vfor :electric conductors, and more particularly vto yexpansion joints for ib-uses -employed rin `high volt-age power or fswiitching :stations tor the 'transmission 'of electrical energy.

'Two types yofconstruction are inconirnon use, ene fin Which .the bus isfsuspended, and the :other in which fthe ibus is rigid. The latter is usually considered the mechanically stronger type of construction. However, heretofore `the lrigid ftype olf .bus :construction :has :been found fobjectionable, since stresses and strains are .imposed fon the porcelain or `vother :insulation parts used in the 'bus supports :and Vlnishings. Porcelain is fairly strong in compression, but relative.-

ly .Weak in :resisting shear stresses'. The consequence is that after'jinstallation Aand putting ofthebusinto service','the porcelain parts'are liable'toibecome *broken and result in disaster. The `fstresses' yonithe 'bus fsu-pports are from a number ofcauses.- Among these are :motion io'f the structure' due to Wind, settling vof .structure foundations or columns, :expansion and zcontraction'due Vto temperature changes, and motion of floor slabs zor 'fthe :apparatus itself Aduring 'the opening rand closing tot circuit lbrea'kers.` v

illhe purpose tot the present invention, therefore, is'to provide fa strong, simple, refcient fexpa'nsionijoint :which will =automatically :compensate ytor :stresses Awhich may 'be imposed =.on `porcelain orfother parts of fbus supports. l

`The character yof the invention may be best understood fby vreference to the following description -oif one good zform thereof shown in the accompanying fdravving, wherein: 1 'Fig. 1. is an elevation of a bus run rigidly secured at intervals to post type insulators mounted on a floor slab. said bus run being provided at intervals with expansionl joints embodying the invention; and Fig. 2 on an enlarged scale is a longitudinal section through onev of the expansion joints shown in Fig. 1.

Referring to the drawing,- 1 designates a copper tubular bus rigidly 'fastened by clamps Sito posts 5 which are mounted on and bolted to a floor slab 7 at suitable intervals. Each of the posts is provided with a series of porcelain insulators 9.

Expansion joints 11 are interposedin the Abus at appropriate intervals, two of these varied asfrequired.

`the sleeve 39 by a 'rivet43- joints being shown therein, but -it will vbe understood that the ynumber thereot' may be `Each of these expansion joints comprises a socket or member 13 having a-'st-ud 15 adapted :to enter anre'nd'portion ofthey tubular busandibe secured thereto by a rivet 19.

A vsocket'or lmember 21 has a stud 23 adapted to enter an endportion of `theftubular bus and`be secured thereto by a lrivet 27.

lA flexible conductor element7 in the `present inst-ance, in 'the' form of a fpigtail 29 made `of Ip'laited -fine copper Wire, extends between and yis secured -to the sockets. In the present finstance, an end portion ofthe pigtail extends through a sleeve '31 having a tapered/portion 33 vthreaded to a tapered IportionIof the socket 13 and slotted to permit said tapered portion 33 to contract slightly as it is lscrewed 'into Vthe tapered portion of the socket, xthereby to Yprevent the sleeve `fromunscrewing from lthe socket.

vAnfend of the Jpigtail Inay be upset to form a 'head 35 adapted to bev confined lbetween the inner end of the sleeve 31 and the vbase of fthe socket. The -pigtail may be positively secured to the sleeve r31 by4 a. rivet 37. The'opposite end portion ofthe pigtail extends through asleeve ,39, andthe end thereof is upset tozform a head 41 adapted to be'con'ined between ythe vinnerend of the sleeve '39 and the lbase of the socket .21. r;[=he vpigta'il may be vpositively secured to The sleeve 31 may havea 'fia'redinouth 45, and the sleeve 39'Inay have a flared mouth 47 to .facilitate iiex'ionv of the lp'igtail andppreventV injury thereto on iexion thereof. i l

Altube lor .housing ,49 has an end .portion 51 tapered and threaded Ito lthe socket 2l, and an end portion 53 entered into a counterbore 55 in the socket 13, the construction being such that the tube and rthe socket are in telescopic relation. The end portion 51 of the tube 49 receives the sleeve 39 and engages a jflange 57 on the inner end of said sleeve, theconstruction being such that when the tube 49 is screwed intothe socket 21, the inner end ot the tube will engage the flange 57 and hold the latter' against the base of the socket. The end portion 5l of the tube is slotted to permit it to contract slightly as it is screwed into the socket, thereby to prevent the tube from unscrevving from the socket.

The opposite ends of v the pigtail are pressed against and havey good conducting contact with the bases of v the sockets.

The ends of the sockets are rounded, and the ends of the studs Which project from the sockets are rounded, thereby to prevent y corona losses.

The construction is such that when motion oi the bus supports occurs from any cause, such, for example, as from the conditions above mentioned, the sockets may move toward or from each other, and the pigtail `may bend or straighten Within the ample v should be such that the electrical resistance of the pigtail shall not be greater than the bus. Otlierivisethe pigtail might be heated to a greater degree than the bus and result in melting of the fine copper Wires of thev pigtail. The current passes from one of the bus end portions through the socket stud and the bases of the socket thereat, and

thence directly through the pigtail to the base and stud of the other socket, and on through the tubular end portion of `the bus thei'eat. Thus, the main current passes through the pigtail and practically none of it passes through the tube 49. t Will be observed that the pigtail is so formed that it does not have a loop which might produce a choke coil effect. `The telescopic construcf tion ot the expansion joint and the ease or flexion of the pigtail enable ready expansion and contraction, the pigtail is enclosed Within and protected by the tube and sockets, and the latter may be in alineinent With the bus and not of a` diameter substantially greater than that of the bus. The joint is mechanically strong in construction and of pleasing design. Its electrical resistance is lower than an equal length ot the bus in Which it is interposed, While its current carrying capacity is greaterr than the cross section of the bus; The joint introduces no coioiia or magnetic losses and has nov indue# tive characteristics. It is'positively and rigidly connected to end portions of the bus, and has no soldered or Weak parts. It is evident that an expansion joint such as described herein adequately providcs for the prevention of breakage ofporcelain parts used in bus supporting construction, and thus tends to eliminate delays and damage heretofore caused by shutdowns kdue to breakage oi insulators or bushings.

The parts of the expansion joint desirably may be made oi copper, but it will be understood that said parts maybe formed of any other suitable conductor of electricity.

l/Vhile the expansion jointhas been described herein in respect to its use in a bus secured to post type insulators mounted on a floor slab, it will be understood that it may be employed in busses for oilcircuit break ers, buses for transformers, and in other installations. j; j i i ltvwill be understood that the invention is notlimited to the specific embodiment shown, andthat various deviations may be made therefrom Without departing from the spirit and scope oit' the appendedclaim.

VVh-at is claimed is i .An expansion joint for a rigid lbus suspended between and supported on spaced insulators, comprising a pair of rigid mem# bers adapted for connection With adjacent ends of the bus, a conductor having end por-` tions secured to said members and a` flexible portion extending between said members, and a single rigid externa-l tube extending between said members and enclosing the` flexible conductor, said tube being slidable relatively to at least one of the members on longitudinal movement of the bus, all of said parts being -uninsulatedconductors, and said tube and members being arranged to prevent relative movement thereof transverselyl to their length.

ROBERT C. SCOTT. 

